1. FIELD OF THE INVENTION
This invention relates to a catalyst system, a process for making the catalyst system and a process for olefin polymerization using the catalyst system. More specifically, this invention relates to a catalyst system using a boron alkyl, especially triethylboron, in combination with an aluminum alkyl, especially triethyl aluminum, as a co-catalyst to improve polymerization yield and to control polydispersity.
2. DESCRIPTION OF THE PRIOR ART
Triethylboron is known as a co-catalyst. U.S. Pat. No. 4,980,330 discloses a list of suitable cocatalysts or activators for an inorganic oxide catalyst. The list includes triethylboron among others. The disclosure specifies a range of the ratio of cocatalyst to transition metal of from about 0.1:1 to about 1000:1. There is no disclosure that triethylboron in combination with other co-catalysts or any combination of co-catalyst results in improved polymerization yield or control of polydispersity.
U.S. Pat. No. 4,814,308 discloses a combination of a lithiumalkyl and a boronalkyl as cocatalyst in a Phillips catalysis. Specifically, triethylboron was used with n-butyllithium. There is no disclosure that triethylboron or any boronalkyl was used with an aluminum alkyl.
Japanese Patent Application No.82167567 disclosed the use of the magnesium, titanium, vanadium and aluminum compounds with triethylboron and dibutylether as a catalyst for the copolymerization of olefins. There is no disclosure that triethylboron or any boronalkyl was used with an aluminum alkyl.
Triethylboron is known as a catalyst. The use of triethylboron as a catalyst for the oligomerization of methylene groups from a formaldehyde-zirconocene complex was disclosed in "Developing Molecular Fischer-Tropsch Type Chemistry: The Triethylboron-Catalyzed Oligomerization of Carbon Monoxide-Derived Methylene Groups From a (.eta.2-Formaldehyde)Zirconocene Dimer" by Erker et al, Journal of the American Chemical Society, Vol. 113, No. 6, p. 2330-2332 (1991).
Japanese patent 7244549 discloses a catalyst for propylene having high molecular weight and low degree of crystallinity. The catalyst is a combination of a boron alkyl, specifically triethylboron and a vanadium halide, specifically vanadium tetrahalide.
It would be advantageous to increase polymer yield for olefin polymerization without increasing the amount of aluminum alkyl used which would increase the aluminum residue in the polymer product. It would also be advantageous to control polydispersity by the addition of varying amount of a non-aluminum co-catalyst. It would also be advantageous to use a material which is known to be compatible with olefin polymerization.